Diffusion of hydrogen is a severe problem in all potential fields of application related to hydrogen production and utilization. Particularly demanding conditions exist in nuclear reactors, because of the high temperatures present, and since severe problems arise from the contact with liquid sodium or other corrosive material unavoidable for the operation of the reactor. High temperatures and corrosion resistance have also to be considered in combustion engines utilizing hydrogen. And chemical resistance (inertness) is necessary also in electrochemical processes associated with the production and storage of hydrogen.
In one known method for creating a hydrogen permeation barrier, hydrogen is bound in a hydride, as is discussed in DE 03130906. The hydrides are mainly based on hydride-forming rare earths (e.g., yttrium) or on alkaline earth metals such as calcium and magnesium. These materials form alloys with present container or wall materials.
Permeation of hydrogen through the walls of various components of nuclear reactors is a potential problem in reactor operation. In U.S. Pat. No. 4,314,880, the formation of intermetallic layers of the reactor material by dipping it into molten aluminum and heating up to 800° C. is suggested. The intermetallic compounds achieved by this method form a hydrogen barrier.
In US 2007/0089764, a gas-tight storage and transportation tank is described using also a metal hydride which differs for the different temperature ranges of the utilization.
In US 2007/0089764, furthermore, a thermoplastic polymer containing hydrides is disclosed as a diffusion barrier for hydrogen.
U.S. Pat. No. 6,787,007 discloses an electrochemically active hydrogen barrier consisting of a complete system of anode layer, cathode layer, electrolytic layer and a catalytic layer, activated by a voltage source.
WO 04057051 describes a hydrogen barrier obtained by puls plasma nitridation.
Furthermore, and more closely related to the present invention, the application of permeation barriers in the form of thin films, in particular of films based on ceramic oxides such as the α-phase of aluminium oxide (α-alumina, α-Al2O3), is suggested [1-4]. Such films have a high efficiency in suppressing hydrogen transport. These barriers can be used in many areas where hydrogen diffusion and retention in materials are of concern. Such films can be multi-functional, since they have the potential to serve also as anti-corrosion layers surviving thermal cycling, to withstand high heat and neutron fluxes and to allow the contact with aggressive media [5]. The highest potential to fulfil most of these requirements has α-alumina due to its unique high temperature thermal and mechanical properties.